Cytotoxic T lymphocytes are a subpopulation of T lymphocytes which mediate the immune response of an organism to viral infection or tissue allographs. the lectins from the seeds of Vicia villosa are of considerable interest because an uncharacterized lectin preparation has been reported to bind specifically to a glycoprotein (T145) on mouse cytotoxic T lymphocytes. In preliminary work, three lectins have been purified from V. villosa seeds. These lectins are tetrameric and are composed of two different subunits with distinct carbohydrate binding specificities. Binding of B4 lectin, the predominant lectin in these seeds, to cloned lines of cytotoxic T lymphocytes is considerably increased over binding to resting splenocytes and thymocytes. In this application, the glycoprotein(s) on a clonel line of cytotoxic T lymphocytes and the oligosaccharide protion of this glycoprotein which specifically interacts with V. villosa B4 lectin will be studied in detail. To do this, a V. villosa B4 lectin affinity adsorbent will be prepared and characterized. The glycoproteins on metabolically-labeled cytotoxic T lymphocytes which bind to this adsorbent will be identified by SDS-PAGE and fluorography. Glycopeptides will also be prepared from these cytotoxic T lymphocytes and fractionated by affinity chromatography on the V. villosa B4 lectin-agarose column. Oligosaccharide units will be released from the labeled glycopeptides which interact with the affinity column and their primary structure determined. Once this oligosaccharide structure is elucidated, the biosythetic mechanism(s) by which it arises will be investigated. Finally, an antisera will be raised to the glycoprotein(s) on cytotoxic T lymphocytes which binds to the V. villosa B4 lectin affinity adsorbent. Immunologically similar glycoproteins on resting mouse splenocytes and thymocytes will be identified by immunoprecipitation of solubilized glycoproteins from these cells. If an immunologically similar glycoprotein is present on these cells, structural similarities between the protein portions of the glycoproteins will be characterized by tryptic peptide mapping. These studies will suggest a mechanism by which a glycoprotein with a new oligosaccharide structure is expressed during the differentiation of cytotoxic T lymphocytes and will eventually lead to a better understanding of the function of cell surface glycoproteins and their oligosacchride units on T lymphocytes.